The invention relates to a fuel supply system for a motor vehicle. More particularly, the invention relates to a fuel supply system which recognizes the engine braking (overrunning) condition of the vehicle and which includes the provision for enhancing the engine braking and fuel economy by interrupting the fuel supply during that condition. When engine braking is terminated, the fuel supply is restarted and the engine is supplied with normal fuel and will respond to accelerator pedal pressure. When the fuel supply is shut off, combustion no longer takes place in the engine and, especially during prolonged engine braking, the engine will cool off considerably. The engine temperature may drop below the condensation temperature for fuel so that after fuel supply is resumed, the fuel may at least partially condense at the interior walls of the induction tube and this fact may result in an insufficient or incorrect fuel-air mixture. Engine operation with a mixture which is diminished in this way results in substantial discomfort to the driver and other disadvantages. One of these disadvantages is the incorrect exhaust gas composition due to combustion at insufficient temperature, which leaves toxic components in the exhaust gas.